Self-adaptive and optionally also otherwise adaptable wound dressing

ABSTRACT

An automatically self-adjusting variable permeability providing (AVPP) layer is provided over and in operative interaction with a wound site containing a wound to the integumentary system of a living creature such as the skin of a human patient. The AVPP layer has the capability of automatically changing in respective fluid permeability characteristics provided by respective subregions of the AVPP layer where the changes are in reaction to extant or changed conditions in corresponding micro-zones of the wound site. The automatic self-adjusting behaviors of the respective subregions of the AVPP layer can include providing a faster rate of vapor removal for micro-zones of the wound site that are too wet and providing a slower rate of vapor removal or essentially no vapor removal for micro-zones of the wound site that are too dry.

FIELD OF DISCLOSURE AND PRIORITY CLAIM

The present disclosure of invention relates generally to treatment ofwounds to the integumentary system of a living creature and morespecifically to ongoing treatment of wounds to the skin system of ahuman being or a like skinned other mammal. The disclosure relates yetmore specifically to methods of adaptively controlling the environmentof a wound as conditions in and around the wound site change, where theadaptive control is for promoting optimal healing of the wound even asconditions in the wound site change.

This application claims priority from U.S. Provisional Application No.61/463,732, filed Feb. 22, 2011 by Oleg Siniaguine and Elena Kachiguina,entitled WOUND DRESSING FOR MOIST WOUND HEALING, the entire contents ofwhich application are hereby incorporated by reference.

2a. Cross Reference to Co-Owned Applications

The following U.S. provisional patent application is owned by the ownerof the present application, and its disclosure is incorporated herein byreference:

-   -   (A) U.S. Provisional Application No. 61/463,732, filed Feb. 22,        2011.

2b. Cross Reference to Issued Patents and Early Published Applications

The disclosures of the following U.S. patents and early publications areincorporated herein by reference:

-   -   (A) U.S. Pat. No. 7,910,789, issued Mar. 22, 2011 to Sinyagin;        Dmitriy et al. and entitled “Method for treating wound, dressing        for use therewith and apparatus and system for fabricating        dressing”;    -   (B) U.S. Pub. No. 20110162193 published Jul. 7, 2011 for        Sinyagin; Dmitriy and entitled “Method for Treating Wound,        Dressing for Use Therewith and Apparatus and System for        Fabricating Dressing”; and    -   (C) U.S. Pub. No. 20100241447 published Sep. 23, 2010 for        Siniaguine; Oleg; et al. and entitled “Customization of Wound        Dressing Using Rule-Based Algorithm”.

3. Description of Related Technology

The present disclosure of invention relates to treatment of wounds tothe integumentary system of a living creature and more specifically towound dressings of the type which can adaptively control the environmentor micro-environments within and around a wound site by for examplepreventing certain parts of a healing wound site from prematurely dryingout or getting excessively wet as treatment progresses, while alsopreventing certain other parts from becoming too dry, whereby suchadaptive control of the wound site environment(s) tends to facilitatemoist wound healing.

When a wound to the integumentary system of a living mammal (e.g., humanbeing) occurs, the body tends to react differently over time by first,for example, producing relatively large amounts of liquids in and/oraround the wound site, where the produced liquids tend to accumulate inthe wound and which accumulated liquids are commonly referred to as“wound exudates”. Wound exudates may comprise a mixture of differentsubstances including for example, blood, water, salts, proteins, andbacteria. Various studies of the wound healing process have demonstratedthat, if kept appropriately physiologically moist in appropriatesubregions thereof, a wound tends to heal substantially faster than ifit is allowed to become too dry or too wet, especially in the finalstages of healing. Such a form of controlled-moisture healing isreferred to herein as “controlled moist wound healing”.

Tradition al wound dressings such as cotton gauze pads and the likeoperate to deter the escape from the wound site of moisture (water) in aliquid form, but the moisture tends to nonetheless escape in a vaporform (to evaporate into the ambient air) at an uncontrolled and oftentoo rapid rate, which then causes the wound to dry out too rapidly, thuspreventing optimal moist wound healing to occur when treated with aconventional cotton gauze pad or the like. Therefore, more advancedwound dressings have been proposed in the art for better controlling theescape rate of vapors from the wound site as well as the escape rate ofliquids. However, dressings that are fixed in their design to minimizevapor escape are generally not well suited for appropriately treatingwounds with medium to high exudate production rates, where for thelatter types of wounds, a faster removal rate of exudate-sourced liquidsand/or vapors may be more desirable. At the same time, such fixed designdressings are generally not well suited for appropriately managing thehealthy and/or semi-healthy skin that surrounds the open wound site (theperi-wound skin) because exposure to excessive moisture can damage theperi-wound skin and thereby inhibit rather than promote wound healing.

Heretofore, wound treatment specialists have tried to implementcontrolled moist wound healing protocols by storing on hand, arelatively large inventory of different dressings with respectivedifferent sizes and respective different degrees of moisture absorbency,moisture storage capacity and/or vapor permeability. Under thisparadigm, the health care providing specialists (specialists in woundcare technology) are expected to be frequently checking up on the woundand its healing stage and frequently replacing old dressings with newerand more wound-appropriate newer dressings that address the everevolving state of the healing (or not-healing) wound. In other words,the wound treatment specialists would attempt on a repeated basis tocategorize each individually encountered wound at the time of encounter(e.g., when following up on wound healing progress and changingdressings) and to pick out from their then on-hand inventory of manydifferent kinds of dressings, the dressing that best suites the thenidentified wound category. There are several drawbacks to this approach.First, the health care providing person who applies the first andsubsequent wound dressings needs to be a well trained specialist inwound assessment and treatment. This can be costly. Second, thedressings may need to be changed frequently, which can significantly addto the cost of wound treatment. Additionally, because the human factoris involved, errors may occur in picking out the correct dressing kindeach time the dressing is changed. Finally, a large inventory ofdifferent kinds of dressings has to be maintained and, if a needed typeof fixed-design dressing is depleted from the on-hand inventory, thepatient who then needs application of such a specific and fixed designdressing is out of luck.

In general and heretofore, wound treatment dressings were of fixeddesign relative to spatial and chronological evolution of the individualwound under treatment. Wounds change over time even during one dressingwear. The faster the wound heals, the faster the conditions within thewound site (e.g., exudate production levels, shapes and sizes of varioustissue type micro-zones within the wound site, etc.) change under thesame dressing. Typically, a wound includes at least three distinctspatial zones or areas whose shapes and sizes tend to change over time.These three major zones are sometimes referred to as the wound bed orwound core, the wound edge and the peri-wound skin which surrounds thewound edge. Healthy skin surrounds the wound edge, and althoughtechnically not part of the wound itself, the healthy skin can convertinto being part of the wound if the healthy skin is maltreated duringtreatment of the wound site and its surrounds. The wound bed portion ofthe wound site is frequently subdivided and categorized into micro-zonesor sub-zones, including a heavily exuding sub-zone which exhibits arelatively high intensity of exudate production, a granulating sub-zonehorizontal a substantially lower or minimal rate of exudate production,and an epithelializing sub-zone having no appreciable amounts ofexudates being produced thereat. Ideally, every such differentlycategorized tissue sub-zone should be treated with a specificallymatched set of treatment parameters (including moisture levelparameters). Consequently, for each differently categorized tissuesub-zone, there should be a corresponding wound dressing part thatprovides the desired treatment parameters for thereby implementing anoptimal local micro-environment for the respective tissue sub-zone. Morespecifically, each heavily exudating part of the wound site should beoverlapped by a wound dressing region which provides relatively highlevels of liquid absorption and relatively high rates of vapor release(evaporation) into the ambient air. The high rate of vapor release isdesired in order to avoid accumulation of excessive amounts of liquid inthe heavily exuding part of the wound, where such accumulation tends tobe detrimental to optimal healing. On the other hand, each low ornon-exuding wound part needs to be kept moist but never (or hardly ever)too wet. Excessive drying out (undue desiccation) should be avoided, forexample by designing the corresponding wound dressing region to preventor minimize water vapor loss in the slow and/or not-exuding zones. Theseexemplary design requirements demonstrate how the needs of one sub-zoneof a wound site can contradict those of another and yet the differentsub-zones and their opposed needs typically coexist simultaneously inand around a single wound site.

As time goes by and the wound progressively heals (or as itprogressively gets worse if for example appropriate antibiotics have notbeen applied or if it is unexpectedly re-injured) the zonal geographiesand/or rates of exudate production and/or degrees of epithelializationof the wound site can dynamically change and, ideally, the dressingshould be reconfigured to address these changes in timely fashion.However, heretofore, the state of the art in wound dressings did notprovide an economical and practical means for addressing the divergentzonal treatment requirements typically found in and around a typicalwound and it did not provide an economical and practical means foraddressing the over-time, and sometimes rapid state changes that mayoccur in different sub-zones of the wound site. One example of anunexpected rapid state change in a wound is if the patient accidentlybumps the wound site (with old dressing on it) into a sharp object andthereby re-injures the wound site.

The unexpected extreme injury to the wound site is but one example ofhow a dressing with fixed design may cease to provide appropriatehealing-promoting micro-environments for respective micro-zones of anunexpectedly variable wound site. When a clinician inspects anencountered wound site for the purpose of formulating atreatment-appropriate dressing design for the wound, the clinician ismerely seeing an out-of-the-field snapshot of the wound and of thepatient to whom the wound belongs. At the time of clinical observation,the patient may be unusually anxious and this anxiety may lead to thewound exhibiting more than normal levels of exudate production. Once thepatient leaves the clinic, he or she may calm down and the level ofexudate production may then decrease as a result. However, what thatgenerally means is that the clinician was induced by the distortedsnapshot and in-clinic observation of the wound to provide a wounddressing that provides too fast of a drying action for the wound oncethe latter gets back into the field and the wound therefore heals atless than optimum rate or not at all because micro-zones therein are toodry.

On the other hand, it equally possible that the patient is less anxiousor less agitated while in the clinic and wound exudates less than usualduring the clinical preparation of the dressing. Once the patient getsout into his or her more normal world (the out-of-clinic normalroutines), the patient may become more anxious or agitated due to workstresses for example or exercise routines and then the wound begins toexude at faster rates than were observed in the clinic. What thisgenerally means is that the clinician was induced by the distortedsnapshot and in-clinic observation of the wound to provide a wounddressing that provides too slow of a drying action for the wound oncethe latter gets back into the field. Therefore, once again, the dressingdesign that was fixedly set in the clinical environment provides anon-optimal treatment for the in-field wound. Other examples where thestates of various micro-zones within the wound site may change caninclude ones where the patient consumes alcohol and/or variousprescription drugs or other substances after leaving the clinic andthese consumptions alter the state of the wound. Another example ofwhere exudation rates can change is if the patient's blood pressuresubstantially rises for any of a number of reasons or instead fallsbelow the levels present during the clinical visit. Yet another exampleof where exudation rates can change is if the patient's woundunknowingly got infected while at the clinic and the consequence of theinfection does become apparent until long after the patient has left theclinic. At that point, because no one sees what is going on under thedressing, the changed conditions of the wound go undetected anduntreated.

Given the above, it appears that wound treatment could be made much moreeconomical and practical if a self-adaptive wound dressing could bedeveloped which, not only at the time of initial application,appropriately and respectively absorbs exudates or hydrates atrespective different rates at respective wound sub-zones (micro-zones)that need the respective rates of liquid absorption and vapor releaseinto the ambient, but also that later on, automatically and adaptivelyself-adjusts to match changing wound conditions at respective sub-zonesof the wound site and/or self-adjusts to match changing dimensions ofsuch sub-zones while providing appropriate micro-environments foroptimal promotion of healing for the respective sub-zones having thevarious wound tissue types, including for the wound edge subregions, andthe peri-wound skin sub-zones. Additionally, wound treatment could bemade much more economical and practical if the dressing is designed toassure that healthy skin surrounding the wound site is not damaged bythe dressing. One advantage of an automatically self-adjusting adaptivewound dressing is that the persons applying the dressing to the wound(e.g., health care practitioners) would not have to be sophisticatedexperts in the art of selecting appropriate wound dressing materials(having appropriate treatment characteristics) and appropriately shapingand dimensioning them, and appropriately aligning them to respectiveportions of the wound site. Instead, they would simply apply theblank-slate wise, initially pre-configured dressing to the wound sitewithout worrying about specific alignment and then the self-adaptivedressing would automatically and in concert with the encountered woundsite conditions, automatically configure itself by appropriatelyaltering material characteristics within the dressing to match thetherapeutic needs of the then encountered underlying micro-zones withinthe wound site in such a way that the re-configured material zonesautomatically align with the underlying micro-zones. Moreover, becausethe self-adjusting adaptive wound dressing continues to re-adjust itselfto ever changing conditions within the wound site, the person(s) whoapply the dressing would not have to change dressings as often; and alsothey would not have to keep as large an inventory of different dressingsas they now have to keep on hand because an automatically self-adjustingadaptive wound dressing would custom-tailor itself to the unique needsof each encountered and unique wound (and its unique interiorsubregions) without calling for subjective human judgment. Theself-adjusting adaptive wound dressing would automatically follow alongwith and self-adapt to the unpredictable changes in the wound siteduring the duration of application of the dressing. As mentioned above,one example of an unpredictable change in the wound site during theduration of a dressing wear is if the patient accidently bumps the woundsite (with old dressing on it) into a sharp object and therebyre-injures the wound site whereby one or more wound site subregions thatwere previously non-exuding ones suddenly become heavily exuding onesdue to the new injury inflicted on the otherwise healing wound site. Aconventional dressing that is not self-adaptive could not automaticallyand relatively immediately respond to such suddenly changed conditions.

It is to be understood that this background of the related technologysection is intended to provide useful background for understanding thehere disclosed technology and as such, the technology background sectionmay and probably does include ideas, concepts or recognitions that werenot part of what was known or appreciated by those skilled in thepertinent art prior to corresponding invention dates of subject matterdisclosed herein.

SUMMARY

In accordance with one aspect of the present disclosure of invention, anautomatically self-adjusting variable permeability providing (AVPP)layer is provided over and in operative interactive coupling relationwith a wound site containing a wound to the integumentary system of aliving creature such as the skin of a human patient. The AVPP layer hasthe capability of automatically changing in respective fluidpermeability characteristics provided by respective subregions of theAVPP layer where the changes are in reaction to extant or changedconditions in corresponding micro-zones of the wound site. The automaticself-adjusting behaviors of the respective subregions of the AVPP layercan include providing a faster rate of vapor removal for micro-zones ofthe wound site that are too wet and providing a slower rate of vaporremoval or essentially no vapor removal for micro-zones of the woundsite that are too dry. The automatically self-adjusting variablepermeability providing (AVPP) layer may form part of a wound treatmentdressing applied to an underlying wound site. The dressing mayadditionally include a liquid-impermeable but vapor breathing (LIVB)layer disposed above the AVPP layer and a liquid absorbing layer or paddisposed under the AVPP layer. In operation, the liquid absorbing layertransmits to respective subregions of the AVPP layer, fluids that, ifpresent, are indicative of tissue states of the micro-zones of theunderlying wound site and the AVPP layer automatically andself-adjusting wise provides corresponding fluid permeabilitycharacteristics for appropriately keeping the respective micro-zones asnot too wet and not to dry for sake of promoting healing of the wound.

BRIEF DESCRIPTION OF THE DRAWINGS

The below detailed description section makes reference to theaccompanying drawings, in which:

FIG. 1 is a schematic cross sectional view of an automatically adaptive(and optionally manually further adaptable) wound dressing according toone aspect of the present disclosure of invention;

FIG. 2 is a schematic cross sectional view of another embodiment havingfirst and second vapor permeable layers where at least one of the vaporpermeable layers exhibits an adaptively programmable MVTR profile;

FIG. 3 is a schematic cross sectional view of another embodiment havinga first vapor permeable layer spaced inwardly from the outer perimeterof a second and overlying vapor permeable layer;

FIG. 4 is a schematic cross sectional view of another embodiment havinga second vapor permeable layer attached to the absorbing core;

FIG. 5 is a schematic cross sectional view of another embodiment havinga spacer disposed between the first and second vapor permeable layers;

FIG. 6 is a schematic cross sectional view of another embodiment havinga third vapor permeable layer;

FIG. 7 is a schematic cross sectional view of a further embodimenthaving a second absorbing layer disposed above theautomatically-variable permeability providing (AVPP) layer; and

FIG. 8 is a schematic cross sectional view of yet a further embodimenthaving a fluids lateralizing layer disposed above the second absorbinglayer.

DETAILED DESCRIPTION

With regard to the figures, it is to be appreciated that these are notto scale and the illustrated thicknesses are generally exaggeratedrelative to the illustrated lateral widths of the dressings. The terms,upper and lower will be used herein as relative terms that areapplicable to the case where the dressing is positioned as shown in thedrawings with one layer being disposed above a next and so forth.Flipping the dressing upside down or otherwise (e.g., at other angles)does not alter the relative, upper versus lower; or above versus belowdesignation given herein to the various layers. Similarly when variousfluids are stated herein to be drawn “up” for example or spread out“laterally” (horizontally) for example, those designations are also tobe understood as relative terms. Flipping the dressing upside down orotherwise (e.g., at other angles) does not alter the relative, up versusdown; or lateral versus vertical designations given herein to thevarious fluid flow directions.

Referring to FIG. 1, a first example of an automatically adaptive wounddressing 1 in accordance with the present disclosure is depicted thereinby an exemplary cross sectional view. The from-the-above top plan view(not shown) may take on many different shapes, dimensions orconfigurations that generally comport with the illustrated and exemplarycross sectional view of FIG. 1, where the latter cross sectional viewmay be taken along a desired sectioning line or sectioning curve drawnon the top plan view (not shown). More specifically, in FIG. 1 thedressing 1 is shown to comprise a liquid(s) adsorbing pad 2, a firstvapor permeable layer 3 and a second vapor permeable layer 4 stackedover one another in the recited order. Of importance, in the variousembodiments the first and second vapor permeable layers 3 and 4 are notof identical function. The first vapor permeable layer 3 may be madepermeable to liquids (e.g., liquid water) as well as being permeable tovapors (e.g., water vapor) while the second vapor permeable layer 4 isnot permeable to liquids. Both of the first and second vapor permeablelayers, 3 and 4 may be made impermeable to molecules and/or to particlessubstantially larger than H2O molecules, for example to bacterial cellsor cell fragments. Although the first and second layers, 3 and 4, arefrequently referred to herein as vapor permeable layers, from time totime the second layer 4 will also be referred to as a“liquid-impermeable but vapor breathing” (LIVB) layer 4. On the otherhand, the first mentioned layer 3 will also be referred to herein as an“automatically-variable permeability providing” (AVPP) layer 3 forreasons that will shortly become apparent.

The absorbent pad 2 is permanently (nondetachably) attached to at leastone of the first and second vapor permeable layers, 3 and 4, and in theillustrated case of FIG. 1 it (2) is shown to be so attached to a lowerfirst side 5 of the first vapor permeable layer 3. The second vaporpermeable layer 4 (a.k.a. the liquid-impermeable but vapor breathing(LIVB) layer 4) is bonded to an upper second side 6 of the first vaporpermeable layer 3. In one embodiment, parts (e.g., removable strips ordots) of the upper or second vapor-permeable/liquid-impermeable layer 4(LIVB) are detachably bonded to the underlying layers or films and maybe manually and/or by machine-means, selectively removed (e.g., byscratch or peel-off removal) so as to thereby alter local fluid (vapor)exhaust rates there-at.

In the same or another embodiment, parts (e.g., micro-zones) of thefirst vapor permeable layer 3 (a.k.a. the automatically-variablepermeability providing (AVPP) layer 3) are time-release wise and/orconcentration of exposure-wise changed by having been exposed to achange-triggering concentration or amount of moisture (e.g., a vaporand/or liquid that triggers chemical change in AVPP layer 3) whereby, atfirst; before they are exposed to a sufficient amount of moisture, therespective micro-zones will exhibit a comparatively low rate of vaportransmission (a low MVTR, as shall be defined below) but after havingbeen exposed over time to a sufficient amount of moisture (e.g., asufficient concentration of a particular type of liquid for a sufficientlength of time), they will exhibit a comparatively higher rate of vaportransmission (higher MVTR) so to thereby automatically increase amoisture-removal rate provided for the wound site tissue below them. Andthen later, after local moisture concentration drops below apredetermined level, the variable parts (micro-zones) of the first vaporpermeable layer 3 (the AVPP layer) will revert to exhibiting acomparatively lower rate of vapor transmission (lower MVTR) so tothereby automatically prevent excessive drying out of the wound sitesub-zones below them after a desired amount of local moisture-removalhas occurred. This low, high, and then low-again vapor transmission ratebehavior is particularly useful for proper treatment of the peri-woundskin and epithelializing parts of the wound site. The latter two partsshould be progressively growing inward towards the center of the woundsite while the respective moisture levels in those respective sub-zonesare kept optimal for those zones to keep growing inwardly and thuscontinue the healing process. More specifically, the outer periphery ofthe peri-wound skin zone generally calls for a drier but not aridmicro-environment while the zones inward of the peri-wound skin zonetypically call for a wetter micro-environment. During healing, theboundary between the two zones advances (travels) inwardly as the woundheals and thus the optimal but different micro-climates for the twozones should spatially advance inwardly with their respective wound sitezones.

The liquid absorbing pad 2 operates to draw excessive exudate away fromthe wound site and to store components (e.g., drawn up bacterial cells)of the removed exudate apart from the underlying wound site. The liquidabsorbing pad 2 may include one or more of hydrophilic fibrous or foammaterials which can readily absorb (bind to them) substantial quantitiesof water or aqueous solutions and store drying out components of theabsorbed and drawn up liquids. The pad 2 preferably comprises anon-woven fabric such as an air-layered or meltspun or electrospun rayonor polyester, or polyvinyl alcohol (PVA) and/or its ethylene copolymers,or other hydrophilic synthetic or natural polymers and materials usefulfor adsorption and absorption of substantial quantities of water oraqueous solutions. The absorbent pad 2 may contain embedded gellingfibers or particles (globules) of super-absorbent polymers (e.g.,polyacrylamide or polyacrylate such as those marketed by EmergingTechnologies, Inc., Greensboro, N.C.) or other known hydropolymers thatbind water (e.g., alginates, reprocessed cellulose, crosslinked or highmolecular weight polyethylene oxide, polyvinylpyrrolidone). Theabsorbency of the pad material is preferably at or higher than 10grams-of-absorbed liquid per gram of absorbent (≧10 g(L)/g(A)) for, forexample, a 0.9% sodium chloride and calcium chloride solution that isconsidered to be close to the composition of typical wound exudate.Absorption Capacity may be measured according to the DIN EN 13726-1standard. In one embodiment, the absorbency of the pad materialprogressively increases as one moves upwardly (e.g., in the +Zdirection) in the cross-sectional view of FIG. 1 whereby the effect isthat initially encountered exudates are rapidly drawn up and away fromthe wound site for storage in, and for drying out within the upper partsof the liquid absorbing pad 2 while later encountered exudates (e.g.,those with fewer amounts of bacteria and/or dirt) are more slowly drawnup into the lower sections of the pad 2. One of the reasons that slowerabsorption rates may be desirable after initial absorption of exudatesis so that the micro-environment of the underlying wound zone does notbecome too dry after the initially large amount of exudate has beentaken up. In one embodiment, the absorbent pad 2 exhibits a directionalabsorption preference that favors drawing liquids more so in the upwarddirection (e.g., in FIG. 1) rather than laterally so that liquids drawnup from a first sub-zone of the wound site tend to not flow laterallythrough the absorbent pad 2 and thereby appear to higher layers (e.g., 3and 4) of the dressing as if the liquids had instead been drawn up froma laterally spaced apart, other sub-zone of the wound site.

The absorbent pad 2 material may include antimicrobial additives, likebroadly used silver and silver salts, polyaminopropyl biguanide (PAPB),polyhexamethylene biguanide (PHMB), polyhexamethylene guanide orpolyhexanide, or other known in the art antimicrobials, antisepticsand/or preservatives in known and recommended for use concentrationsthat are non-cytotoxic, typically 0.01-0.5% by weight.

The absorbent pad 2 may include embedded hygroscopic liquids forproviding a desired degree of fiber and/or particle softening so thatthe dressing can easily flex when applied to the wound site. Preferably,the embedded hygroscopic liquid is polypropylene glycol or glycerin. Theamount of hygroscopic liquid is preferably 0.001-0.05 g/cm², and morepreferably 0.005-0.03 g/cm².

The absorbent pad 2 may initially be pre-charged with an embeddedquantity of sterile water (or saline solution) for irrigating andmoisturizing the wound site at an initial stage of wound treatment. Theamount of water in the absorbent pad 2 may be about 50-80 weight %.Preservatives like benzyl alcohol 0.9% or 0.085% chlorhexidine gluconateor 0.02% bronopol may be added to the water pre-charge. In oneembodiment, the pre-charged irrigation liquid(s) is/are stored inpressure frangible beads which break open when sufficient pressure isapplied to them. More specifically, the user may be instructed to kneadthe packaging that holds the dressing before taking out the dressing andapplying it to the wound site. (See for example US Pub 2007/0020320“Wound dressing and methods of making and using the same”, David et alwhich is incorporate herein by reference.)

The absorbent pad 2 may initially be pre-charged with an embeddedmixture of water and hygroscopic liquid. The percent of hygroscopicliquid in the water-glycerin mixture may be about 5-75% w (by weight),and more preferably 10-30% w. The amount of water-hygroscopic liquidmixture initially provided within the absorbent pad 2 may depend on thepercentage of hygroscopic liquid in the mixture, and may be such thatthe resulting amount of water in the absorbent pad 2 is 10-80 weight %.The resulting amount of water or aqueous solution initially providedwithin the absorbent pad 2 may be less than the maximum absorptioncapacity of the absorbent pad 2. One function of such an initiallyprovided pre-charge of water or aqueous solution may be to irrigate thewound site with sterile liquid prior to or at the same time as beginningto absorb exudate. As indicated above, the initial irrigating liquid(s)may be stored in frangible beads or the equivalent embedded within theabsorbent pad 2 and released when the pad is kneaded by hand or byappropriate machine means.

The absorbent pad's vertical thickness and lateral length and widthdimensions may vary depending upon the intended use for the dressing.The thickness of the absorbent pad 2 may be between 1 and 3 mm orthicker, preferably 1.5-2 mm. The dressing is typically made in a rangeof sizes: 5×5 cm, 10×10 cm, 15×15 cm, 20×20 cm as measured in thelateral directions. Therefore the lateral dimensions are substantiallylarger than the vertical thickness. The shape of the absorbent pad (asseen in the top plan view) may be rectangular or oval or another shapespecifically applicable to a particular part of a human body where thedressing is to be applied to. In use, the lower major surface of theabsorbent pad 2 engages directly or indirectly with the wound site whilethe second vapor permeable layer 4 (the liquid-impermeable but vaporbreathing (LIVB) layer) interfaces with the exterior air. The serialcombination of the first and second vapor permeable layers, 3 and 4,controls the rate of vapor exhaust from the interior of the dressing andinto the ambient air. The upper vapor permeable layer 4 may optionallyhave parts that can be selectively detachably removed from the lowervapor permeable layer 3 (or from lower film layers of the second vaporpermeable layer 4 itself) in the form of rectangular strips or circularones of concentric rings or otherwise so that, for example, quick detachremoval or scratching away of more central and upper film parts of theupper vapor permeable layer 4 (e.g., those at or closer to the centralsurface area of the dressing) will result in a dressing that has higherrates of vapor exhaust nearer to the central and more heavily exudatingcore of the wound site while initial non-removal of the more peripheralstrips or rings of the upper vapor permeable layer 4 result in adressing that has lower rates of vapor exhaust at or near the peripheralareas of the wound site (e.g., above the peri-wound skin and surroundinghealthy skin). As time progresses, the outer removal rings (of layer 4)may be progressively removed to promote further drying around the outerperiphery of the peri-wound area as the latter advances (grows) inwardlyduring the course of typical wound healing. In one embodiment, ascratch-resistant, but fluid passing mesh (not shown) is interposedbetween a top and optionally detachable film of thevapor-permeable/liquid-impermeable layer 4 and a lower but notdetachable film of the same layer 4 (films not separately shown). Theoptional, scratch-resistant mesh (not shown) protects the lower filmfrom being removed even as the upper one is scratched or peeled away. Inthis way, the general liquid-impermeable but vapor breathing (LIVB)properties of the second vapor permeable layer 4 are substantiallypreserved.

In another embodiment (FIG. 2), the wound-facing bottom side 60 of theabsorbent pad 2 is covered with a wound-contacting layer 61, where thewound-contacting layer 61 rather than the absorbent pad 2 defines adirectly wound-contacting face of the dressing. The wound-contactinglayer 61 is permanently (e.g., nondetachably) attached to the absorbentpad 2. The wound-contacting layer 61 may be made of a pre-sterilizedliquid permeable mesh or perforated film or liquid permeable non-wovenfabric. The wound-contacting layer 61 should be made of a material thatis biocompatible with the wound site and may be made of a synthetic orbiologic or bioabsorbable polymer or their combinations. Examples ofsuch polymers include nylon, polyethylene, polyvinyl alcohol (PVA),ethylene vinyl acetate and/or ethylene vinyl alcohol copolymers, whichare typically non-adherent to the wound tissue. The wound-contactinglayer 61 should be perforated or porous to allow for the passagetherethrough of wound moisturizing liquid and/or exudate liquid and/orwound moisturizing vapor. The thickness of the wound contact layer 61may be in the range of about 5-500 microns and the pore size may be inthe range of 0.1-1000 micron. The wound contact layer 61 material mayinclude antimicrobial additives, like broadly used silver and silversalts, polyaminopropyl biguanide (PAPB), polyhexamethylene biguanide(PHMB), polyhexamethylene guanide or polyhexanide, or other known in theart in concentrations that are non-cytotoxic, typically 0.01-0.5% w.

In one embodiment, the whole of the automatically-variable permeabilityproviding (AVPP) layer 3 is at least partially or completely soluble inwater and/or in specific other liquids such that if respectivesub-portions of layer 3 are exposed to wet exudate for example, therespective sub-portions will partially (e.g., proportionally) or fullydissolve into the surrounding liquid and thereby automatically createcorresponding areas of increased vapor permeability (faster vapor escaperates) in the dressing. In an alternate embodiment, first vaporpermeable layer 3 (e.g., that of FIGS. 1 and 2) instead includesspatially distributed material spots 10 that are at least partially orcompletely soluble in water and/or in specific aqueous liquids such thatif they are exposed to wet exudate for example, they will partially(e.g., proportionally) or fully dissolve into the surrounding liquid andthereby automatically create corresponding areas of increased vaporpermeability (faster vapor escape rates) in the dressing. Other portions(11) of the automatically-variable permeability providing (AVPP) layer 3are not dissolvable or substantially less easily dissolvable. Thedissolving of the spots 10 and/or respective sub-portions of theautomatically-variable permeability layer 3 need not create a throughhole at the spot (e.g., 10) where the dissolving occurs but rather suchdissolving may instead create a region of reduced film thickness. Suchreduced film thickness correlates with a higher MVTR. Additionally, thedissolving of the spots 10 and/or respective sub-portions of layer 3 tothe point where through holes are created may cause the lower or firstvapor permeable layer 3 to become permeable to liquids as well as towater vapor. This occurs if the amount of dissolution at spots 10 (orother dissolvable sub-portions of layer 3) is large enough to createthrough holes. In other words, liquid permeability is induced when thelocal concentration of a hydrolyzing liquid (e.g., exudate) issufficiently high and is present for a sufficiently long time (andoptionally also has a required level of acidity or other chemicalattribute) to completely eat through a significant portion ofhydrolyzable polymer bonds present at that spot 10 (or other alikesub-portion). Examples of materials which can be tailored to have suchcharacteristics include polyvinyl alcohol (PVA), poly ethylene oxide,poly vinyl pyrrolidone and other known polymers and/or their blends orco-polymers with various degrees or cross-linkage breakability orhydrolyzation-ability being integrated into the characteristics of thepicked polymer. As used herein, the “degree” of cross-linkagebreakability or hydrolyzation-ability measures the proportion of locallypresent polymer bonds that can be broken by a correspondinghydrolyzation process. (As understood in the chemical arts,hydrolyzation is a chemical process resulting in bond decomposition,where the process involves the splitting of the bond and the additionto, or substitution at the location of the broken bond of a hydrogencation and a hydroxide anion in place of the bond; where the H⁺ and OH⁻substitutes may be obtained from surrounding water molecules forexample.)

The first vapor permeable layer 3 may be made in the form of anon-porous film (a solid film through which gases may diffuse butliquids cannot flow) having alternating spots 10 of hydrolysable(soluble) material and surrounding mesh areas 11 of non-hydrolyzable(non-soluble) material each with a thickness of about 25-300 microns. Inembodiments where upper film strips of upper layer 4 are additionally,optionally detachable, the detachable upper portions preferably overlaponly the non-dissolvable mesh portions 11 of the lower, first vaporpermeable layer 3 so that open holes (for bacteria to get in) will notbe created by combined complete dissolution of the hydrolyzable materialspots 10 of the first vapor permeable layer 3 and optional detachment ofthe detachable portions of the upper, second vapor permeable layer 4.

The first vapor permeable layer 3 (the automatically-variablepermeability providing (AVPP) layer 3) may be made of theabove-mentioned materials which initially have relatively low MoistureVapor Transmission Rates (MVTR) such as <1000 g/m2/24 Hour, preferably<500 g/m2/24 H, when the material is dry (it has not yet been exposed toa hydrolyzing liquid), and it has a substantially increased MVTR, forexample >1000 g/m2/24 Hour when the material has been exposed to ahydrolyzing solution (e.g., exudate) for a sufficiently long timeduration. Therefore subregions of the dressing that are exposed at layer3 to exudate absorbed thereto from a corresponding subregion of thewound site and for long enough of an exposure period will adaptively andautomatically convert to dressing subregions of relatively higher vaportransmission (e.g., MVTR>1000 g/m2/24 Hour) while subregions of thedressing that are not exposed at layer 3 to large concentrations ofexudate absorbed thereto from a corresponding subregion of the woundsite and/or for not long enough of an exposure time will remainsubstantially in their initial and relatively low MVTR state (e.g.,MVTR<500 g/m2/24 H). In other words, the dressing automatically andadaptively self-adjusts according to the degree of exudate absorbed fromeach respective micro-zone of the wound site and transmitted to acorresponding hydrolyzable material spot (e.g., spot 10) of the firstvapor permeable layer 3. In one embodiment, the lower, first vaporpermeable layer 3 also automatically becomes increasingly more permeableto small-sized liquid molecules (e.g., H2O) when exposed over time tosufficient concentrations of a hydrolyzing solution (e.g., exudate). Theadvantage of this aspect will be discussed when the spacer-includingembodiments of FIGS. 5 and 6 are discussed later below.

MVTR (Moisture Vapor Transmission Rate) may be measured according to theDIN EN 13726-2 standard. (DIN is a German abbreviation which in Englishmeans the German Institute for Standardization.)

In one embodiment, the dissolvable spots 10 of the first vapor permeablelayer 3 include temperature-dependent spots 10 which are made of one ormore materials that are soluble only in above-room-temperature water oraqueous solution with a temperature for example that is >25° C. Morespecifically, the hydrolyzing solution (e.g., exudate) may be heated toabove normal room-temperature by the patient's body heat (and/or byanother heat providing means—e.g., an electric heating element). Anexample of such a temperature-sensitive material may be polyvinylalcohol (PVA) with 60-80% degree of hydrolyzation, where here, thepercent of hydrolyzation indicates what proportion of available polymerbonds are broken by prolonged exposure at temperature to the hydrolyzingsolution.

The upper or second vapor permeable layer 4 may be made of a nonporousfilm or non-woven fabric with a relatively low moisture vaportransmission rate (MVTR) or it may be made of multilayer combinations ofnon-woven fabric and nonporous film materials permanently and/ordetachably bonded together to provide a desired MVTR for that secondvapor-permeable/liquid-impermeable layer 4. The thickness of the secondvapor permeable layer 4 may be in the range of about 10-150 microns, ormore preferably 50-100 microns. The material of the second vaporpermeable layer 4 may include polyethylene, polypropylene, polyesterand/or poly vinyl acetate.

Of importance, the upper or second vapor permeable layer 4 should bemade of a liquid impermeable and microorganism impermeable material thatnonetheless transmits vapor with an MVTR >1000 g/m2/24 H. By contrast,the lower or first vapor permeable layer 3 may be composed of one ormore materials that, when converted by hydrolyzation; do permit smallsized liquid molecules (e.g., H2O) to permeate through them butpreferably still block larger sized particles (e.g., microorganisms)from permeating through.

Laminations of thin polyurethane films may be used to meet the abovepreferred characteristics for the second vapor permeable, but liquidimpermeable layer 4. The films of layer 4 may each have a thickness ofabout 10-50 microns and may provide MVTR's up to 3000 g/m²/24 hoursdepending on composition and thickness. Preferably, the film or filmsfor second layer 4 is/are chosen to exhibit an MVTR greater than 2000g/m²/24 hrs while still being impermeable to liquids. In one embodiment,if multiple films are used for forming the second vapor permeable layer4, they are provided with respective different colors, for example redand blue with the blue covering the red (and a scratch resistant meshbeing optionally interposed between). A user may scratch off orotherwise selectively remove the upper and first colored film to therebyexpose the lower and differently colored film of the liquid impermeablelayer 4 (optionally through a see-through scratch resistant mesh). Bythis means, the user (e.g., health care provider) can readily see whatpattern of selective increase of MVTR for water vapor is being providedby the manually programmed (or machine-wise automatically programmed)selective removal of part of the top of layer 4. In one embodiment, anexposed red color is understood to mean a higher MVTR while blueindicates a lower rate.

Hydrophobic non-woven fabrics and micro-porous membranes (e.g., thosemarketed by the 3M™ Company) with pore sizes of 0.1 micron or less arealso micro-organism impermeable and resistant to passing water and waterbased liquids but provide relatively high MVTR due to their openmicro-pore structures. Polypropylene or other hydrophobic polymers maybe the material of choice for non-woven layer or micro-porous membrane.Typical thickness of the non-woven film for layer 4 or a membranethereof is 50-500 microns.

The second vapor permeable but liquid impermeable layer 4 may be made asa multi-layer stack of films and non-woven fabrics permanently ordetachably bonded together (not shown in Figs). Such stacks may helpminimize the inconvenience of thin film handling but still preserve thedesired high MVTR rating for the second layer 4.

The first vapor permeable layer 3 is preferably bonded to the absorbingpad 2 with a porous adhesive (not shown on the Figs.) where the porousadhesive has open cell pores after curing and thus allows for passage ofliquid therethrough. The pore size of the cured adhesive may be 0.1-200microns. The more preferred pore size is 0.1-10 microns. (An example ofsuch an open pore adhesive is a porous adhesive marketed by AdhesiveResearch, Inc., Glen Rock, Pa.).

It will be appreciated that the vapor permeable layers 3, 4, theabsorbent pad 2 and wound contact layer 61 could be manufactured and/orlater cut to have any suitable shape and dimensions such as 3×5 inchrectangular, circular, oval, triangular or other specific to aparticular part of a human or animal body and the shape and size of thewound site.

Other adaptive dressings in accordance with present disclosure ofinvention may comprise one or more additional vapor permeable layersplaced on top of and/or below the second vapor permeable layer 4. Theadditional layers may have the same or similar features as said secondvapor permeable layer 4, including optional, non-automatic (e.g.,manual) programming of the MVTR in different areas of the dressing'supper surface.

The respective outer perimeters of the absorbent pad 2 and the first andsecond vapor permeable layers 3 and 4 may be laterally coextensive withone another, i.e., vertically superimposed (see FIGS. 1-2), so that theentire upper surface area of the absorbent pad 2 is covered in thelateral directions by the first and second vapor permeable layer 3 and4. In a variation, the peripheries of one or both of the first andsecond vapor permeable layers 3 and 4 may extend beyond the lateralperiphery of the absorbent pad 2 so that sidewalls of the absorbent pad2 are covered by at least one of layers 3 and 4.

The permanent attachment of the absorbent pad 2 to the first vaporpermeable layer 3 can be made by lamination, or by extruding the filmmaterial of layer 3 directly onto the absorbent pad 2 material, or byelectrospinning of fibrous material of the absorbent pad 2 directly onthe material of the first vapor permeable layer 3. If lamination isemployed, the lower, first side 5 of the first vapor permeable layer 3may be coated with a pressure sensitive (pressure activated) adhesive(not shown in the Figs.). This attachment adhesive should have an MVTRthat is not less than the MVTR of the first vapor permeable layer 3.That may be achieved by using a patterned adhesive with >50% of the openarea. (An example is a patterned pressure sensitive adhesive, marketedby SCAPA, Inc. of Inglewood, Calif.)

As mentioned above, some segments or spots 11 of the first vaporpermeable layer 3 may be made non-soluble (FIG. 2) to water or aqueoussolutions. This may be achieved by patterned localized crosslinking ofthe polymers by known thermal, chemical, ultraviolet and/or irradiationmethods. Localized crosslinking of a polymer film may be achieved bymasking of the to-be-left-as soluble film areas 10 prior to and duringchemical, thermal or irradiation exposure. The non-soluble areas 11 aredistributed, preferably, uniformly laterally and as a structurallyintegrated mesh along at least the top surface area of the first vaporpermeable layer 3 with area sizes 0.01-20 mm, and coverage of 10-90% oftotal combined area of the top surface area of the first vapor permeablelayer 3.

The first vapor permeable layer 3 may be made by coextrusion of a watersoluble polymer as mentioned above and of a water resistant (nonsoluble)polymer (polypropylene, polyethylene, poly vinyl acetate, etc). In thiscase, the areas 11 of water resistant polymer are distributed,preferably, uniformly laterally along the first vapor permeable layer 3with area sizes 0.01-20 mm, and 10-90% of total combined area.

In another embodiment, the periphery of the first vapor permeable layer3 is spaced inwardly (as shown in FIG. 3) for 1-30 mm, preferably, 20 mmfrom the lateral outer perimeter of the second vapor permeable layer 4.The second vapor permeable layer 4 is directly bonded to the absorbingpad 2 near the periphery of the absorbing pad 2. In this case, since theperiphery of the dressing is not covered by all of layers 3 and 4, butrather by a fewer number (e.g., one) of vapor permeable layers, theperiphery of the dressing exhibits a higher MVTR and thus allows theperiphery of the wound site to be drier than the core.

In another embodiment, the first vapor permeable layer 3 is providedwith through openings 7 (FIG. 4). The openings 7 in layer 3 may have alateral size (e.g., diameter of) 0.4-5 mm, and may be of various shapes,and may be uniformly distributed over the total lateral surface areaconsumed by the first vapor permeable layer 3. The combined area of thethrough openings 7 should be less than 20%, and more preferably lessthat 5%, of the consumed surface area of first vapor permeable layer 3.The second vapor permeable layer 4 is directly bonded to the absorbingpad 2 through the openings 7. The bonding adhesive used in openings 7may be a porous one or a non-porous one depending on whether thedressing is designed to intentionally let vapors escape through thebonding openings 7 (and then through vapor permeable layer 4) or not.

Referring to FIG. 5, in another embodiment, an open cells, porous orperforated spacer layer 12 may be interposed between the first vaporpermeable layer 3 and the second vapor permeable layer 4. Preferably,the spacer layer thickness is about 10-250 microns, the pore size 13 is1-100 microns with 5-90% of open void area. The open cell pores oropenings 13 may provide lateral liquid communication between each other.The spacer layer 12 may be made for example of a porous adhesivemarketed by Adhesive Research, Inc. of Glen Rock, Pa.). The spacer layer12 may be made by dots of an adhesive material that bonds with the firstvapor permeable layer 3 and bonds with the second vapor permeable layer4 (an example is MacTac™ glue dots marketed by MacTac, Inc. of Stow,Ohio). Although not specifically shown, the automatically-variablepermeability layer 3 includes hydrolyzable material whereby itspermeability at local spots to vapors and/or liquids changes whenexposed for sufficiently long time to a hydrolyzing liquid (e.g.,exudates). When a large concentration of exudates is present at a givensub-zone for a long time, the hydrolyzable layer 3 automatically breaksdown at that location and then the exudate escapes through the brokendown area to spread laterally into the pores of the porous or perforatedspacer layer 12. This increases the lateral surface area by way of whichvapors from the laterally spread liquid can permeate throughvapor-permeable/liquid-impermeable layer 4 and out into the ambient. Therate of evaporation is thus automatically increased.

Referring to FIG. 6, in another embodiment, the function of the firstautomatically-variable permeability providing (AVPP) layer 3 may beprovided by two or more spaced apart layers such as 15 and 16 separatedfrom each other by an open cells porous or perforated spacer layer suchas 17. Preferably, each layer 15 and 16 has a thickness of 10-250microns, the pore size 20 is 1-100 microns with 5-90% of open void area.The respective MVTR variability characteristics of the spaced apartlayers 15 and 16 need not be the same. The open cell pores or openings20 of spacer layer 17 may provide lateral liquid communication betweeneach other. The spacer layer 17 may be made of porous adhesive marketedby Adhesive Research, Inc., USA. The spacer layer 17 may be made by dotsof an adhesive material that bonds well with each of layers 15 and 16(an example is MacTac™ glue dots marketed by MacTac, Inc. USA). In theembodiment of FIG. 6, the spacer layer 12 between automatically-variablepermeability layer 16 and vapor-permeable/liquid-impermeable layer 4 isalso present.

In one embodiment, prior to employment at a wound site, the dressing 1is packaged in a moisture and micro-organism impermeable pouch, sealedand pre and/or post sterilized by any of known in the art methods likegas sterilization or gamma or electron beam irradiation. The dressingpackaging may include indicia identifying the dimensions, shapes MVTRranges and liquid storage capacities of the enclosed dressing.

To apply the dressing to a wound, the user (e.g., health care provider)opens the sterile pouch, orients it so that the wound contact layer 60faces the wound, and positions the lower surface 61 of the wound contactlayer against the wound so that the wound center approximately coincideswith the dressing center. The upper surface of the dressing may includecentering indicia such as crosshair lines that may be lined up withcrosshair line extensions drawn on healthy areas of the patient's skinoutside of the per-wound areas.

In the case of FIGS. 3-6 where the second vapor permeable layer 4extends peripherally beyond the first vapor permeable layer 3 so that ahigher MVTR is provided in the peripheral areas of the wound site, themoisture (e.g., water vapor) output from the peri-wound skin area israpidly exhausted through the areas covered only by the first vaporpermeable layer 3 so that the healthy skin area surrounding the woundsite remains relatively dry. An occasional droplet of perspirationgenerated at the peri-wound skin or healthy skin area may be is absorbedby the co-extent absorbent pad 2 and thereafter evaporated through theimmediately overlying second vapor permeable layer 4 of the peripheralzone. As a result, the mini-environment over the peri-wound and healthyskin areas remain appropriately dry without accumulation ofskin-damaging liquid thereat. This helps prevent skin maceration.

If an encountered wound is identified as low exuding or has no exudates(low drainage), the limited moisture (exudate, secretion, water vapor)from the wound bed is absorbed by the absorbent pad 2 but moisture vaporevacuation (exhaust) from over the wound bed and out to the ambient airis constrained by the presence of the non-hydrolyzed first vaporpermeable layer 3 which initially has a relatively low MVTR and stays inthat state if not hydrolyzed by absorbed and upwardly drawn exudates. Asa result, when the encountered wound zone conditions are that of therebeing no or relatively low levels of exudates, the initially low MVTR ofthe automatically-variable permeability layer 3 remains low, themicro-environment over the wound bed is therefore kept moist and of arelatively high-humidity where the latter prevents desiccation of thesurface of the wound bed and this facilitates optimal conditions forinward cell growth proliferation (from the surrounding peri-wound areas)and thus rapid wound healing. The presence of the low MVTR, first vaporpermeable layer 3 over the peri-wound areas also supports a relativelyhigh or medium humidity environment over the wound edge and this helpsto prevent wound edge desiccation and/or damage to newly epithelializedskin.

If, on the other hand, a given part of a wound site is highly exuding(high liquid production rates), the exudates are absorbed by theabsorbent pad 2 over that part of the wound site and drawn up intocontact with the automatically-variable permeability layer 3. The vaporevacuation (exhaust to the outside) is initially slow in this regionbecause of the vapor flow restricting, serial combination of the firstand second moisture vapor permeable layers 3 and 4, where the serialcombination exhibits a low combined MVTR. As absorption begins, thewater portion of the exudates mixture is initially bound to thesuperabsorbent or hydropolymer particles of fibers in the absorbing coreof pad 2 so that initially there are no free flowing water particles inthe pores between the superabsorbent particles and fibers.

If and when the amount of liquid absorbed by the pad 2 becomessufficiently large after some time (e.g., after the dressing is worn bythe patient for a predetermined number of hours), the absorbed liquidsaturates the water binding capacity of the water-binding material andsubsequently, free-flowing (unbound) water will appear in the spacesbetween the water-binding particles and/or fibers of the absorbent pad2. Eventually this unbound liquid rises to and reaches the first vaporpermeable layer 3. In the case where the first vapor permeable layer 3includes the hydrolyzable material spots 10, exposure of these spots 10to the free flowing liquid (e.g., water, exudates) in growing amountstriggers disintegration (dissolving) of the hydrolyzable parts of thefirst vapor permeable layer 3, where this disintegration adaptivelyoccurs generally over only the heavily exuding parts of the wound siteand not over the non-exuding or lightly exuding parts. In one variation,the absorbent pad 2 is provided with an anisotropic absorbency profile,for example at least partly up in the upper heights of the absorbent pad2 so that the liquids from the heavily exuding parts of the wound siteare inhibited from cross flowing laterally through the absorbent pad 2to cause unintended disintegration of the hydrolyzable material spots 10that are disposed over the drier micro-zones of the wound site. As aresult, the drier micro-zones are prevented from becoming too dry due toexcessive vapor exhaust (into the ambient) over their respective areaswhile the heavily exudating micro-zones of the wound site are preventedfrom becoming too wet thanks to the automatically increased vaporexhaust rates (into the ambient) caused by selective disintegration ofthe hydrolyzable material spots 10 that are disposed over the wettermicro-zones. In one embodiment, the hydrolyzable material spots 10 arenot homogenous over each micro-zone but rather distributed as fasterdissolving (more readily disintegrating) and more slowly dissolvingspots 10 so that the automatically induced increase of MVTR will beautomatically proportional to the length of time that the spots 10 ofdifferent hydrolyzing rates are exposed to hydrolyzing liquid and or tothe concentration levels and/or chemistries (e.g., alkalinity) of thelocally present hydrolyzing liquids. In other words, once the vaporexhaust rate of a given micro-zone increases to match the liquidproduction rate of its underlying portion of the wound site, the liquidconcentration levels in that subregion drop so as to no longer exposethe remaining spots 10 (those with slower hydrolyzing rates) to ahydrolyzing concentration of the liquid and the automatic process ofprogressively disintegrating more and more of the harder-to-hydrolyzematerial spots 10 automatically comes to a substantial stop. Thus eachmicro-zone of the wound site is automatically kept from becoming eithertoo wet or too dry.

In the case of the spacer-including structures of FIGS. 5-6, even if agiven micro-zone in the wound site is both small in area and high inexudation rate, when the excess liquid crosses through the first vaporpermeable and also converted-into-being a liquid permeable layer 3, thepermeating-through liquid spreads out to cover a larger lateral surfacearea by passing through the open cell pores of the spacer layer(s) 12and/or 17 so that the spread out liquid is provided with a larger uppersurface area from which its vapors may evaporate into the ambient by wayof the liquid impermeable but vapor permeable layer 4. In other words,since the second vapor permeable layer 4 is liquid impermeable, when theliquid gets into the natural capillaries or gaps, formed by spacer 12between the first and second vapor permeable layers 3 and 4, the liquidspreads out laterally. Then, however, the liquid impermeable layer 4blocks the liquid from leaking out to the outside of the dressing.However, because of the MVTR of the second vapor permeable layer 4 ishigh, the evaporation rate of water vapor through the upper, secondvapor permeable layer 4 sharply increases due to the expanded lateralsurface area provided for such evaporation and as a consequence, thisreduces the accumulation rate of liquids in portions of the absorbingcore 2 that overlie heavily exudating micro-zones of the wound site evenif those heavily exudating micro-zones, on their own, have relativelysmall surface areas.

By providing the first vapor permeable layer 3 of FIG. 6 as being madeof a combination of two or more spaced apart soluble films 15 and 16with porous spacers in between, a more gradual increase of the rate ofwater vapor evaporation from the dressing may be provided for. Morespecifically, the rising liquid spreads out laterally in area by a firstproportional amount when it reaches the lower spacer layer 17 and thenthe reduced concentration of liquid controls the subsequentdisintegration of the hydrolyzable material spots 10 (not shown) ofpermeable layer 16. Yet more specifically, a time delay function may beprovided wherein; if the wound exuding intensity was high for a shorttime immediately after the wound was created and then it later becomesmuch reduced, then only one layer 15 is dissolved by immediate exposureto the high concentrations of exudating liquid, and due to time delay inthe liquids advancing to the next successive layer 16, its respectivehydrolyzable material spots 10′ (not shown) will remain more intact andthus prevent too high of a water evaporation rate from developing wheresuch a too-high of an evaporation rate can lead to undesired wound partover-desiccation.

The material of the first vapor permeable layer 3 may form a viscousliquid when it is fully disintegrated by the hydrolyzing liquid(s) ofsufficient concentration. After the hydrolyzing liquid(s) recede (due toevaporation of their water component for example), the left-behindviscous liquid formed by the fully dissolved hydrolyzable material spots10 (not shown) is confined to remaining between, and drying out betweenthe absorbing pad 2 and the second vapor permeable, but liquidimpermeable layer 4. If the intensity of wound exudates discharge ratenext becomes reduced, the dried out remnants of the viscous liquid will,upon completion of their drying out process, automatically form anonporous film that works to reduce further water vapor loss from theabsorbing pad 2 at that spot and ultimately reduce moisture loss fromthe less-exuding wound bed thus automatically providing for a moistenvironment for the underlying wound site subregions even if beforehand,those subregion were heavily exuding ones and now they are less exudingones. Small pores of the spacers 12, 17 and the bonding layer betweenthe absorbing pad 2 and the first vapor permeable layer 3 help todistribute the high viscous liquid more uniformly by locking the liquidin the pores. That results in forming more uniform, vapor blocking filmsas drying of the viscous liquid pools occurs.

When the lateral spacer layers (e.g., 12 and/or 17) are present, even ifthe first vapor permeable layer 3 is dissolved as a small spot only overa small, but heavily exuding part of the wound site, the rising columnof exudate liquid will be driven up by capillary forces through the onesmall spot so as to be is quickly spread out laterally into a muchlarger lateral area between the first and second vapor layers 3 and 4 byaction of the one or more spacer layers. This process significantlyincreases the area of evaporation through the second vapor permeablelayer 4. In other words, the relatively high MVTR of the second vaporpermeable but liquid impermeable layer 4 combined with the largerevaporation surface area provided to the laterally spreading outportions of the rising column of liquid exudate provides a relativelyhigh water evaporation rate, that then automatically reduces liquidaccumulation in the absorbing core 2 and increases the useful wear timeof the dressing 1. As a consequence, dressings in accordance with thepresent disclosure need not be changed as often as the non-adaptivetraditional dressings and costs of providing health care services may besignificantly reduced.

By spacing the edge of the first vapor permeable layer 3 laterallyinward relative to the dressing 1 edge (e.g., FIG. 3), the healthy skinaround the wound site is preserved and the wear time of the dressing maytherefore be increased. One of reason for frequent dressing changes maybe that undesired leakage of exudates from the dressing periphery (edge)tends to damage the surrounding healthy skin. However, in theembodiments where the first vapor permeable layer 3 is spaced inwardfrom the dressing edge, lateral spreading of exudate liquid between thelayers 3 and 4 is blocked from occurring at the dressing edge. Thisprevents undesirable leakage of a potentially corrosive and infectiousliquid (e.g., bacteria containing exudate) from the dressing edge wheresuch leakage may then require more frequent wound cleanings and morefrequent change of the dressing even before the absorbing core 2 reachesthe limits of its absorbing capacity. In other words, the full exudateabsorbing capacity of the absorbent pad 2 may be exploited due to acombination of advantageous operations of the here disclosed,automatically-adaptive wound dressing 1. Excess moisture is quicklyevaporated away as needed so that the absorbent pad 2 does not becomeprematurely saturated with water and damaging leakage of exudate to thehealthy skin surrounding the wound site is prevented so that thefrequency of dressing changes may be reduced. In the mean time, theabsorbent pad 2 collects and stores the non-water components of thewound site exudates to basically the full exudate absorbing capacity ofthe absorbent pad material. Hence, the absorbing capacity is efficientlyutilized to its full extent.

It is possible for the laterally spreading liquid between the first andsecond vapor permeable layers 3 and 4 to fully disintegrate the firstvapor permeable layer 3 if the latter layer is fully hydrolyzable. Thatmay result in undesirable delamination of dressing layers and loss ofdressing integrity. Therefore in at least some of the illustratedembodiments (e.g., FIG. 2), the non-hydrolyzable (e.g., water resistant)segments 11 are provided so as to define an integrity maintaining meshthat keeps the first vapor permeable layer 3 well bonded to theunderlying absorbing pad 2 and keeps the second vapor permeable layer 4also bonded to the structure, thus preventing loss of dressingintegrity. Although not shown in the other figures, it is to beunderstood that the concept of the integrity maintaining mesh 11 isequally applicable in those other embodiments. Alternatively oradditionally the illustrated bonding in FIG. 4 of the second vaporpermeable layer 4 directly to the absorbing pad 2 through the providedbonding openings 7 provides another means of maintaining dressingintegrity. One or both of these integrity maintaining techniques may beused in the others of the illustrated embodiments.

If the first vapor permeable layer 3 is made of a material that issoluble only in warm water (temperature >25° C.), then the triggering ofdissolution of the first vapor permeable layer is the results of thesimultaneous effects of two factors: presence of free flowing liquidbetween the superabsorbent particles and fibers, and thetemperature >25° C. (preferably 28-32° C.) of the first vapor permeablelayer 3.

A wound bed tissue temperature is close to the normal human bodytemperature of 36.6° C. Moreover, the fibrous or foam structure of theabsorbing pad 2 defines is a relatively good thermal insulator. As aresult, a significant temperature gradient tends to develop between thewound bed tissue and the first vapor permeable layer 3; for example withtemperature dropping from 36.6° C. (or higher if the patient has afever) to ambient room temperature as vertical distancing away from thewound bed tissue and closer to the vapor-permeable/liquid-impermeablelayer 4 progresses for rising droplets of exudate liquid. As a result,if no warm exudate rapidly rises through the absorbent pad 2, thetemperature of the first vapor permeable layer 3 remains close to theambient temperature (usually room temperature 18-22° C.) and theautomatically-variable permeability layer 3 is not converted into ithigh MVTR mode. On the other hand, if the wound site is heavily exudingwarm liquid and that warm (above room temperature) liquid rapidlyreaches the first vapor permeable layer 3, the latter layer 3 quicklydisintegrates at that spot and allows for high rates of vapor release.

When all the absorbed liquid is bounded to superabsorbent particles andfibers and no free flowing water has yet formed, there are still a lotof air in the empty cells between fibers and particles of the absorbingpad 2, the thermal insulation characteristics of the pad 2 are preservedand a significant difference in temperature continues to exist betweenthe wound bed and the first vapor permeable layer 3 temperature. Thismaintained thermal insulation helps to assure that a correspondinglylower temperature is maintained at least for a while for parts of thefirst vapor permeable layer 3 that are disposed over non-exuding orlow-exuding zones of the wound site. Accordingly, even if a column ofwarm exudate breaks through one part of layer 3 and spreads laterallybetween the first and second layers, 3 and 4, and over the non-exudingor lesser exuding parts of the wound site, a cooling of the upwellingwarm and spreading out exudate occurs due to water evaporation and heatconductivity to the ambient air through the liquid-impermeable but vaporbreathing (LIVB) layer 4 and also due to thermal inertia whereby thelaterally spaced apart areas of layer 3 are initially kept cool helps toprevent undesired disintegration of the first vapor permeable layer 3over the these non- or less-exuding parts in spite of the presence oflaterally spreading out liquid between the first and second layers, 3and 4, and over these parts of the wound dressing. In other words, thetemperature-dependent disintegrating characteristics of theautomatically-variable permeability layer 3 help to provide for thefollowing: a) to continue providing a controlled moist air environmentover the non-exuding parts of the wound due to the still intact firstvapor permeable layer 3 above them; b) to reduce the probability ofover-wetting of non-exuding wound parts and/or peri-wound skin and/orsurrounding healthy skin due to the blocking of undesired leakage of theexcessive liquid from the heavily exuding wound part and into contactwith the drier parts; d) to reduce or minimize the probability ofinfection or re-infection of the non-exuding (e.g., more healed) woundparts and peri-wound skin due to bacteria being transferred togetherwith the spread out exudate liquid from the exuding wound part.

Referring to FIG. 7, shown here is another embodiment, similar to thatof FIG. 5 except that in FIG. 7, a second liquid absorbing layer 22 isdisposed above and in contact with the automatically-variablepermeability providing (AVPP) layer 3. The second liquid absorbing layer22 may be made of same or similar materials as that the first liquidabsorbing layer 2 (a.k.a. absorbent pad 2) and/or of differentmaterials. The second liquid absorbing layer 22 may be of a homogeneouscomposition laterally thereacross and/or vertically therethrough or itmay vary in composition and/or absorbency characteristics eitherlaterally thereacross, or vertically therethrough or in both senses. Thethickness and/or absorbency capacity of the second liquid absorbinglayer 22 need not be the same as that of the first liquid absorbinglayer 2 (a.k.a. absorbent pad 2) and at least in one embodiment, thesecond liquid absorbing layer 22 is thinner and has a lower absorbencycapacity.

One possible function for the second liquid absorbing layer 22 is todraw fluids (e.g., permeability altering liquids and/or vapors) awayfrom the top side of the automatically-variable permeability providing(AVPP) layer 3 such that the permeability of AVPP layer 3 is controlledessentially by the concentration, amounts and/or chemistries of thefluids (e.g., permeability altering liquids and/or vapors) transmittedto its lower side by the first liquid absorbing layer 2 (a.k.a.absorbent pad 2) and not substantially by fluids that appear near theupper side of the AVPP layer 3. With that said, it is nonetheless withinthe present contemplation of the disclosure that in an alternateembodiment, fluid concentrations at the upper side of the first AVPPlayer 3 (e.g., those representative of humidity in the ambient air) doalter the permeability of the first AVPP layer 3 (or alternatively of asecond AVPP layer such as layer 16 of FIG. 6). In the case where thefunction of the second liquid absorbing layer 22 is to draw fluidsvertically away from the upper surface of the first AVPP layer 3 of FIG.7, the absorbency of the material in the second liquid absorbing layer22 may increase as one progresses vertically up through that layer 22 asshown in FIG. 7. Capillary action may quickly pullpermeability-affecting fluids away from the top side of the first AVPPlayer 3 and towards proximity with the liquid-impermeable but vaporbreathing (LIVB) layer 4 above it so that vapors from the verticallydrawn up fluids exhaust into the ambient air by way of LIVB layer 4. Asin the case of FIG. 6, it is within the contemplation of the presentdisclosure to have two or more spaced apart automatically-variablepermeability providing (AVPP) layers (e.g., like 15 and 16 of FIG. 6),where in the case of FIG. 7 (or that of next described FIG. 8) thesecond AVPP layer (not shown in FIGS. 7-8) is disposed above the secondliquid absorbing layer 22 (and/or above the lateral fluids dispersinglayer 17 of FIG. 8). That second AVPP layer (not shown in FIGS. 7-8)would respond variably to the concentration, amounts and/or chemistriesof the fluids (e.g., permeability altering liquids and/or vapors)transmitted to its lower side by the second liquid absorbing layer 22(and/or the lateral fluids dispersing layer 17 of FIG. 8).

Referring to FIG. 8, shown here is a further embodiment, similar to thatof FIG. 7 except that in FIG. 8, a lateral fluids dispersing layer 17(e.g., similar to 17 or 12 of FIG. 6) is provided above the secondliquid absorbing layer 22. Once absorbing layer 22 has drawn fluidsvertically up and away from the first AVPP layer 3, the lateral fluidsdispersing layer 17 distributes those vertically transmitted fluids(e.g., liquids and/or vapors) laterally over a wider surface area sothat vapors of these may more quickly be exhausted into the ambient airby way of liquid-impermeable but vapor breathing (LIVB) layer 4.

It is to be appreciated that the above are merely illustrative examplesand that those skilled in the art, after having appreciated the presentdisclosure, will be enabled into seeing many additional variations. Ingeneral, one of the aspects taught herein is that one or moreautomatically-variable permeability providing (AVPP) layers like 3and/or 15-16 may be provided above a wound site having respectivemicro-zones that exhibit different tissue types (e.g., heavily exuding,lightly exuding, epithelializing, etc.); that fluids representative ofthe current states of those respective micro-zones may be verticallytransmitted up to corresponding sub-portions of at least the first AVPPlayer 3 where the first AVPP layer 3 is structured to variably alter itspermeability in the corresponding sub-portions according to theconcentration, amounts and/or chemistries of the fluids (e.g.,permeability altering liquids and/or vapors) transmitted at least to itslower side, and as a result; a wound site treatment mechanism isprovided that variably responds to the tissue-type representing fluidicsignals sent to it from the respective micro-zones of the wound sitebelow.

WORKING EXAMPLES Example 1

A wound dressing in accordance with the disclosure was made bylaminating of the following layers: 1) a wound contact layer 61 made ofcross-linked polyvinyl alcohol fibers, the polymer was blended withantimicrobial additive polyhexamethylene biguanide (PHMB) 0.3 w %, thelayer thickness was 150 microns, the layer density was 0.1 g/cm3, thefiber diameter range was 0.5-2 micron; 2) the absorbent pad 2 was madeof polyester fibers with super-absorbent polymer particles (materialbeing designated as WoundFelt™ marketed by National Nonwoven, Inc,Easthampton, Mass.), the layer thickness was 1.2 mm; 3) the first vaporpermeable layer 3 was made of polyvinylpyrrolidone (marketed byScientific Polymers, Inc, USA), had a thickness of 150 microns, aninitial MVTR of 400 g/m2/24 hours when dry; 4) the second vaporpermeable layer 4 was made of polyurethane high MVTR film (Bioflex™,marketed by SCAPA corporation, USA), had a film thickness of 25 microns,an MVTR of 2500 g/m2/24 hours). The layers 61, 2, 3 and 4 werepermanently bonded to each other by patterned pressure sensitiveadhesive (Rx560U™, marketed by SCAPA corporation, USA). The size of theso-fabricated dressing was 100×100 mm, the shape was a square withrounded corners having a radius of 15 mm.

Example 2

The wound dressing per Example 1 and further modified such that theabsorbent pad 2 contained a pre-charge of sterile water at a density of0.15 g/cm2 and glycerin at 0.03 g/cm2.

Example 3

The wound dressing per Example 2 further modified such that the firstvapor permeable layer 3 was made of two polyvinylpyrrolidone films(marketed by Scientific Polymers, Inc, USA) each having a thickness of150 microns, and an MVTR of 400 g/m2/24 hours when dry. The films werebonded to each other by a porous adhesive (marketed by AdhesiveResearch, Inc., Glen Rock, Pa.) having a thickness of 50 microns, a poresize of 20-250 microns, and an open area percentage equal to about 40%.

The present disclosure is to be taken as illustrative rather than aslimiting the scope, nature, or spirit of the subject matter claimedbelow. Numerous modifications and variations will become apparent tothose skilled in the art after studying the disclosure, including use ofequivalent functional and/or structural substitutes for elementsdescribed herein, use of equivalent functional couplings for couplingsdescribed herein, and/or use of equivalent functional steps for stepsdescribed herein. Such insubstantial variations are to be consideredwithin the scope of what is contemplated here. Moreover, if pluralexamples are given for specific means, or steps, and extrapolationbetween and/or beyond such given examples is obvious in view of thepresent disclosure, then the disclosure is to be deemed as effectivelydisclosing and thus covering at least such extrapolations.

Reservation of Extra-Patent Rights, Resolution of Conflicts, andInterpretation of Terms

After this disclosure is lawfully published, the owner of the presentpatent application has no objection to the reproduction by others oftextual and graphic materials contained herein provided suchreproduction is for the limited purpose of understanding the presentdisclosure of invention and of thereby promoting the useful arts andsciences. The owner does not however disclaim any other rights that maybe lawfully associated with the disclosed materials, including but notlimited to, copyrights in any computer program listings or art works orother works provided herein, and to trademark or trade dress rights thatmay be associated with coined terms or art works provided herein and toother otherwise-protectable subject matter included herein or otherwisederivable herefrom.

If any disclosures are incorporated herein by reference and suchincorporated disclosures conflict in part or whole with the presentdisclosure, then to the extent of conflict, and/or broader disclosure,and/or broader definition of terms, the present disclosure controls. Ifsuch incorporated disclosures conflict in part or whole with oneanother, then to the extent of conflict, the later-dated disclosurecontrols.

Unless expressly stated otherwise herein, ordinary terms have theircorresponding ordinary meanings within the respective contexts of theirpresentations, and ordinary terms of art have their correspondingregular meanings within the relevant technical arts and within therespective contexts of their presentations herein. Descriptions aboveregarding related technologies are not admissions that the technologiesor possible relations between them were appreciated by artisans ofordinary skill in the areas of endeavor to which the present disclosuremost closely pertains.

Given the above disclosure of general concepts and specific embodiments,the scope of protection sought is to be defined by the claims appendedhereto. The issued claims are not to be taken as limiting Applicant'sright to claim disclosed, but not yet literally claimed subject matterby way of one or more further applications including those filedpursuant to 35 U.S.C. §120 and/or 35 U.S.C. §251.

What is claimed is:
 1. An adaptive wound dressing comprising: a liquidabsorbing pad having respective upper and lower major surfaces; aliquid-impermeable but vapor breathing (LIVB) layer disposed above theliquid absorbing pad; and a first automatically-variable permeabilityproviding (AVPP) layer interposed between the liquid absorbing pad andthe LIVB layer; wherein the first AVPP layer has a capability toautomatically change at least in terms of a respective degree of fluidpermeability provided by at least one portion thereof to a first classof fluids when that at least one portion thereof is subjected to atleast one of the same first class of fluids or to a different secondclass of fluids in sufficient quantity and/or concentration and/or for asufficient length of time; and wherein said automatic change capabilityof the at least one portion of the first AVPP layer with regard to thedegree of fluid permeability of the at least one portion of the firstAVPP layer includes a capability to change whereby the at least oneportion of the first AVPP layer initially switches from having a firstpermeability corresponding to a relatively low, first vapor transmissionrate, to having a second permeability corresponding to a relativelyhigher and second vapor transmission rate, and to thereafter switchingfrom having the second permeability to having a third permeabilitycorresponding to a third vapor transmission rate that is lower than thesecond vapor transmission rate.
 2. The adaptive wound dressing of claim1 wherein: said automatic change capability of the at least one portionof the first AVPP layer with regard to the degree of fluid permeabilityprovided by the at least one portion of the first AVPP layer includesswitching from being impermeable to liquids to being permeable toliquids.
 3. An adaptive wound dressing comprising: a liquid absorbingpad having respective upper and lower major surfaces; aliquid-impermeable but vapor breathing (LIVB) layer disposed above theliquid absorbing pad; and a first automatically-variable permeabilityproviding (AVPP) layer interposed between the liquid absorbing pad andthe LIVB layer; wherein the first AVPP layer has a capability toautomatically change at least in terms of a respective degree of fluidpermeability provided by at least one portion thereof to a first classof fluids when that at least one portion thereof is subjected to atleast one of the same first class of fluids or to a different secondclass of fluids in sufficient quantity and/or concentration and/or for asufficient length of time; and wherein the at least one portion of thefirst AVPP layer initially has a nonporous first micro-structure of afirst predetermined thickness that is permeable to vapor but not toliquids.
 4. The adaptive wound dressing of claim 3 wherein: the at leastone portion of the first AVPP layer responds to being subjected to atleast one of the first and second classes of fluids by switching fromhaving said initial nonporous first micro-structure of the firstpredetermined thickness to having a post-exposure nonporous secondmicro-structure of a smaller second thickness that is more permeable tovapor but still not permeable to liquids.
 5. An adaptive wound dressingcomprising: a liquid absorbing pad having respective upper and lowermajor surfaces; a liquid-impermeable but vapor breathing (LIVB) layerdisposed above the liquid absorbing pad; and a firstautomatically-variable permeability providing (AVPP) layer interposedbetween the liquid absorbing pad and the LIVB layer; wherein the firstAVPP layer has a capability to automatically change at least in terms ofa respective degree of fluid permeability provided by at least oneportion thereof to a first class of fluids when that at least oneportion thereof is subjected to at least one of the same first class offluids or to a different second class of fluids in sufficient quantityand/or concentration and/or for a sufficient length of time; and whereinsaid automatic change capability of the at least one portion of thefirst AVPP layer with regard to the degree of fluid permeability is atemperature dependent one.
 6. The adaptive wound dressing of claim 5wherein: the automatic change capability provided by the at least oneportion of the first AVPP layer is one that does not initially occuruntil the respective at least one portion of the first AVPP layer issubjected to at least one of the first and second classes of fluids andwhile at a minimum temperature greater than at least 20 degrees C. 7.The adaptive wound dressing of claim 6 wherein: the minimum temperatureis at least 28 degrees C.
 8. The adaptive wound dressing of claim 6wherein: the minimum temperature is at least 32 degrees C.
 9. Anadaptive wound dressing comprising: a liquid absorbing pad havingrespective upper and lower major surfaces; a liquid-impermeable butvapor breathing (LIVB) layer disposed above the liquid absorbing pad;and a first automatically-variable permeability providing (AVPP) layerinterposed between the liquid absorbing pad and the LIVB layer; whereinthe first AVPP layer has a capability to automatically change at leastin terms of a respective degree of fluid permeability provided by atleast one portion thereof to a first class of fluids when that at leastone portion thereof is subjected to at least one of the same first classof fluids or to a different second class of fluids in sufficientquantity and/or concentration and/or for a sufficient length of time;and wherein an initial fluid permeability provided by the least oneportion the first AVPP layer before automatically changing in degree offluid permeability provided to the first class of fluids is about orless than 1000 g/m²/24 Hours.
 10. The adaptive wound dressing of claim 9wherein: a subsequent fluid permeability provided by the least oneportion the first AVPP layer after automatically changing in degree offluid permeability provided to the first class of fluids issubstantially greater than 1000 g/m²/24 Hours.
 11. An adaptive wounddressing comprising: a liquid absorbing pad having respective upper andlower major surfaces; a liquid-impermeable but vapor breathing (LIVB)layer disposed above the liquid absorbing pad; and a firstautomatically-variable permeability providing (AVPP) layer interposedbetween the liquid absorbing pad and the LIVB layer; wherein the firstAVPP layer has a capability to automatically change at least in terms ofa respective degree of fluid permeability provided by at least oneportion thereof to a first class of fluids when that at least oneportion thereof is subjected to at least one of the same first class offluids or to a different second class of fluids in sufficient quantityand/or concentration and/or for a sufficient length of time; and whereinprior to operatively engaging with a wound site, the liquid absorbingpad has one or more initial pre-charge liquids or gels embedded therein.12. The adaptive wound dressing of claim 11 wherein: the one or moreinitial pre-charge liquids or gels embedded in the liquid absorbing padincludes at least one of a hygroscopic liquid, a sterile salinesolution, water, and an antimicrobial liquid or gel.
 13. The adaptivewound dressing of claim 12 wherein: the one or more initial pre-chargeliquids or gels embedded in the liquid absorbing pad includes glycerinas a component thereof.
 14. The adaptive wound dressing of claim 11wherein: a quantity of the one or more initial pre-charge liquids orgels embedded in the liquid absorbing pad prior to said operativeengagement with a wound site is less than a maximum liquid absorbingcapacity of the liquid absorbing pad.